Zane Mellor, Peter Dodt, Jalailah Jayne-Maree Jones, Addison Stewart, Jye Sheehan and Chace Harrison died during end-of-year celebrations at Hillcrest Primary School in Tasmania in December 2021.
Rosemary Gamble, the operator of Taz-Zorb which set up the castle and inflatable items, is facing a court hearing for allegedly failing to comply with work health and safety duties.
Six children died when a "mini-tornado" hit the jumping castle they were playing on. (HANDOUT/TASMANIA POLICE)
Gamble has pleaded not guilty, with her lawyer Chris Dockray saying no measures suggested by the prosecution would have prevented the outcome.
Several witness statements from teachers and students read to Devonport Magistrates Court on Tuesday described a "mini-tornado" on an otherwise calm day.
In opening submissions, prosecutor Madeleine Wilson said the school's principal described a strong breeze coming out of nowhere.
The castle was lifted two-three metres in the air before it went "flying" 75m to the other side of the school oval.
One witness said the castle spun around in circles, while a girl who was getting a drink said she heard screams and turned around to see "everything go up into the air".
Another child said she saw a friend fall to the ground.
A man living near the school saw the castle being tossed around. He then heard a large bang and saw it wrapped around a tree.
Statements from teachers and students described a "mini-tornado" on an otherwise calm day. (Bianca De Marchi/AAP PHOTOS)
Five of the children died after falling from a height, while Addison was struck with an electronic blower. Three other children suffered serious injuries.
It is alleged Gamble did not take all reasonable steps to ensure the children weren't exposed to a risk of serious injury or death and failed to ensure the castle was properly anchored.
The castle was tethered at four of its eight anchorage points, not in line with the manufacturer's manual, Ms Wilson said.
"She had sufficient pegs to be able to do that, and it was easy to do," Ms Wilson said.
None of the pegs met Australian standards requiring a minimum 16mm diameter and were instead 10mm, she said.
It is also alleged Gamble failed to properly train and supervise the two Taz-Zorb workers, one of them her partner, who were with her at the school.
Correct tethering would have likely prevented the anchorage failing completely, Ms Wilson said.
Chris Dockray said had the castle been tethered with eight pegs the outcome wouldn't have changed. (Ethan James/AAP PHOTOS)
Gamble, who was charged in November 2023, had operated the castle at least 100 times previously at markets, fairs and schools.
Mr Dockray said Gamble had, prior to purchasing, obtained an assurance from the jumping castle's manufacturer that it complied with Australian standards.
The manufacturer "supplied no manual whatsoever" but Gamble downloaded a one-and-a-half page guide from the company's website.
Mr Dockray said the instructions were ambiguous and the company only provided four stakes.
The "sudden dust storm" could not have been anticipated and even if the castle was tethered with eight pegs the outcome would have been the same, he said.
Mr Dockray said a 13-page manual on the manufacturer's website, relied on by the prosecution. had gone up online after the incident.
The hearing, expected to last two weeks, will also hear from weather, safety and engineering experts as well as the other two Taz-Zorb workers.
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